Method for insolubilizing spun protein filamentary products



Jan. 12, 1954 R. H. K. THOMSON 2,665,966

METHOD FOR .msowsruzmc SPUN PROTEIN FILAMENTARY PRODUCTS Filed July 9,1951 Robin Jiamz'li'on Kizdall Thom-9oz;

Patented Jan. 12, 1954 METHOD FOR IN SOLUBILI-ZIN G SPUN PRO- TEINFILAMENTARY PRODUCTS Robin H. K. Thomson, to Imperial Ghemi'ca Fairlie,Scotland, assignor l Industries. Limited, a cor-- porationof.Great-Britain.

Application July 9, 1951, Serial No. 235,718

Claims priority, application Great-Britain August 28, 1950 Claims.

The present invention relates to a new or improved method forinsolubilising artificial filaments, threads, fibres and the likefilamentary products obtained by the spinning of solutions of proteins,for instance, peanut protein or. casein, in aqueous alkaline or othersuitable aqueous solvent media into suitable acidified. salinecoagulating baths.

In British patent specification No. 597,497. there. is described. and.claimed inter alia a. method of. insolubilising artificial filamentaryproducts obtained by the spinning of solutions. of vegetable seedglobulins, for instance peanut proteins, or phospho-proteins, forinstance casein, in aqueous alkaline or other aqueous solvent mediavinto suitable acidified saline coagulating baths. which.

comprises treating the said filamentary products in an aqueousformaldehyde bath saturated toboth sodium chloride and sodium sulphateor to both sodium chloride and magnesiumsulphate at a pH of 4 to 6 andat a temperature not exceed.- ing 60 C. and thereafter treating thefilamentary products in an aqueous formaldehydebath strongly acidifiedwith sulphuric acid and saturated with sodium sulphate. or magnesiumsulphate at the temperature employed, the saidstrongly acidifiedformaldehyde bath being at a raised temperature.

It is stated therein that the coagulated filaments can first be passedthrough a saturatedsodium chloride bath at approximately C. in whichthey remain until their longitudinal contractility has been greatlyreduced. It is filamentary productswhichhave been thus relaxed which aresubsequently treated in the twoaforesaid baths. The treating liquid inwhichthe filamentary products are thus relaxed will. hereinafter hereferred to as relaxing solutions or relaxing treating liquids.

It has now been found that it is possible to provide a more economicalprocess than hereto fore for the productionof insolubilised proteinousfilamentary products in a period of time lying for instance between 1and minutes and under conditions in which the filaments of a travellingtow remain open and distinct by employing. solutions wherein sodiumsulphate is at least the: main saline constituent. in. the acidified.saline coagulating bath, inthe relaxing solution, inthe formaldehydesolution at pH between 4 and 7,

and in the formaldehyde solution strongly acidified with sulphuric acid.

We are aware that British patent specification No. 623,460 describes andclaims inter alia a method of treating a continuously advancin tow o1filaments by immersion in a treating liquid for a relatively long periodof time by providing a horizontal ring-trough rotatable about a verticalaxis, passing treaung liquid in acontinuous manner through said,ring-trough and rotating the ring-trough with substantially the samedirectional speed as the mean circular velocity attained by the saidtreating liquid in said ringtrough, inducing a vibratory motionsubstantially radial to the centre of the rotating ring-trough in theadvancing tow at a position vertically above the treat-mg liquid,permitting the thus treated swaying advancing tow to fall into thetreating liquid and to form itself therein into folds on thefioor of therotating trough immediately below the region where it enters the liquidand also regulating the speed of rotation of the ring-trough so that onwithdrawing the tow from out of the treating liquid at any desireddistance away from the said region measured along thecircumference ofthe ring-trough the said'tow has remained in the treating liquid for thedesired period of time.

In said patent specification there is disclosed by way of example thecoagulation of an extruded caustic soda solution of groundnut globulinby a coagulating solution containing sodium sulphate as its salineconstituent, the relaxing of.

the continuously advancing tow of filaments in a solution ofsodiumsulp-hate saturated at 1'5 (3.,-

the treatment ofthethus relaxed filaments in a solution of sodiumsulphate saturated at 0; containing lt formaldehyde at pH 5 and thefurther treatment. of the tow in a treating liquor. at a temperature ofC.. and consisting of a solution of sodium sulphate saturated at C.

containing 1 /2970 formaldehyde and 20% sulphuric acid by volume and thesubsequentwashing and drying of the thus treated tow. There is nostatement however that a continuously ad.- vancing tow treated in: thismanner is insolubilised, that isv tosay is resistant to the action of abath containing 6.1% sulphuricacid and 0.25% sodium. sulphate.- when.immersed therein for minutes at 97 C.

It has now been found that in order to produce insolubilised filamentsfor example in accordance with the method of British patentspecification No. 623,460 it is essential that there should be at leasta minimum quantity of a chlorine ion present at least in theformaldehyde solution strongly acidified with sulphuric acid.

In patent specification No. 637,025 there is described and claimed interalia a method for insolubilising. continuously travelling tows ofartificial filamentary products obtained by the spinning of solutions ofvegetable seed globulins, for instance, peanut globulins, or ofphospho-proteins for instance, casein, in aqueous alkaline or otheraqueous solvent media into acidified'saline coagulating baths byadvancing the said continuously travelling tow through a tubular passageby means of a turbulent stream of an aqueous formaldehyde solutionsaturated with sodium chloride and containing sodium sulphateormagnesium sulphate in solution and having a pH of 4 to 6, occupying saidtubular passage, and

thereafter advancing the so treated tow through another tubular passageby means of a turbulent stream of another aqueous formaldehyde'solutionthat is at a higher temperature than the said formaldehyde solution ofpH 4 to 6, this hotter aqueous formaldehyde solution occupying saidother tubular passage and being strongly acidified with sulphuric acidand saturated with sodium sulphate or magnesium sulphate at thetemperature employed. It has been found that as the process proceedsthat the strongly acidified formaldehyde solution becomes moreconcentrated in sodium chloride due to carry-over and that steps have tobe taken to keep the sodium chloride constant in said strongly acidifiedformaldehyde solution for the rate of insolubilisation to be constant.

The object of the present invention is to provide a process which isadapted to insolubilise under non-tensioning conditions a continuouslytravelling tow of protein filaments and in which the filaments of thetravelling tow remain open and distinct by employing a series ofsolutions wherein the total quantity of sodium chloride included anddistributed in the series formed by a relaxing solution having sodiumsulphate as its stipulated saline constituent, a formaldehyde solutionhaving a pH preferably between 4 and 7 and having sodium sulphate as itsstipulated saline constituent and a formaldehyde solution stronglyacidified with sulphuric acid and having sodium sulphate as its mainstipulated saline constituent and sodium chloride as an additionalstipulated constituent at least approaches the minimum quantity requiredfor insolubilisation to occur in a stipulated time lying between aperiod of time of 1 and 30 minutes.

A further object of the present invention is to employ solutions havinga lower concentration of reagents than was heretofore consideredpossible, and particularly with respect to the ooncentration of thereagents in the formaldehyde solution strongly acidified with sulphuricacid thereby effecting economies in the amount of reagents lost due tothe taking up of the solutions by the filaments undergoinginsolubilisation with the subsequent removal by washing of the reagentsthus present in the finally insolubilised filaments.

According to the present invention the method of insolubilising undernon-tensioning conditions in a period of time lying for instance between1 and30 minutes a continuous travelling tow of coagulated filamentsobtained by the spinning of aqueous alkaline solutions of protein intosulphuric acid/sodium sulphate coagulating baths and under suchconditions that the travelling tow remains open and the filamentsdistinct comprises treating the travelling tow of coagulated filamentsin a relaxing solution containing not less than 220 g. of sodiumsulphate per litre of solution, treating the thus relaxed filaments at atemperature not exceeding 80 and preferably above 40 C. in an aqueousformaldehyde solution containing not less than 210 g. sodium sulphateper litre of solution and having a pl-I value preferably between 4 and 7and thereafter treating the travelling tow at a raised temperature in astrongly acidified aqueous formaldehyde solution containing per litre ofsolution not less than 340 g. sodium sulphate, not less than 15 g.sodium chloride, or a quantity of a reagent producing a chlorine ion andequivalent to an amount at least not less than 15 g. sodium chloride,and not less than 200 g. sulphuric acid.

The second formaldehyde bath, i. e. the said strongly acidifiedformaldehyde solution can be used at temperatures higher than 90 thoughpreferably the temperature is between 70 and 98 C.

It is desirable for the treating solutions preceding the said stronglyacidified formaldehyde solution to be free of sodium chloride unless itis required to shorten the time of treatment. Again the higher thequantity of sodium chloride present in the said strongly acidifiedformaldehyde solution the shorter is the time necessary to obtaininsoluoilised protein filaments, i. e. protein filaments which donotdissolve in a solution of r 0.1% sulphuric acid and 0.25% sodiumsulphate when immersed therein for minutes at 97 C.

It will be understood furthermore that in so far as the relaxingsolution and the first formaldehyde solution are concerned, although itis desirable in accordance with the invention not to increase theconcentration of the sodium sulphate to values higher than 220 g. and216 g. respectively, it is nevertheless possible to carry out continuousinsolubilisation in a period of time between 1 and 30 minutes if thesefigures are exceeded.

In so far as the second formaldehyde solution is concerned, it is againdesirable to keep as near as possible to the minimum concentrationsgiven. Here, however, it is necessary to carry out preliminaryinvestigations to ascertain the maxi-- mum values of sodium sulphate andsulphuric acid if the minimum concentration required for the sodiumchloride is exceeded as the sodium chloride, sodium sulphate, andsulphuric acid concentrations are inter-related. A higher concentrationof sodium sulphate can be compensated for by a higher concentration insulphuric acid or sodium chloride or both. A higher sulphuric acidconcentration may be compensated for by a higher sodium sulphate or alower sodium chloride concentration and a higher sodium chlorideconcentration may be compensated for a lower sulphuric acid or highersodium sulphate concentration it being understood that theconcentrations of sodium sulphate, sulphuric acid and sodium chloridemust not be allowed to fall below the minimum concentration stipulatedfor each of these ingredients.

In so far as the first formaldehyde solution is concerned, it isdesirable that the temperature should be above 40 C.

The invention is illustrated by the following example in which the partsare parts by weight except where otherwise indicated-and withreferencetothe diagrammatic drawing accompanying the specification forthe jinsolubilisation in a periodof .15 minutes'o'f a continuous tow ofgroundnut-globulin. 3 1

A solution of groundnut globulin containing 20% globulin, 1.1% sodiumhydroxide and 78.9%

water is extrudedthrough a spinneretj into a coagulating bath 2containing 240 1 g./l. sodium sulphate and 20 g./l. sulphuric acid. Thecoagulated tow 3 is stretched between godets, 5 and then treated for 4minutes with a solution containing 230 g./l. sodium sulphate, at a pH8.5 at 23 to 30 C. contained in the trough of a ringtrough 7 accordingto the method described and claimed in patent specification No. 623,460.This treatment is effected by leading the tow 3 under tension to a godet6 situated vertically above the centre line of the trough of thering-trough 7 through a reciprocating device 8 at least 3 feet above thesurface of the liquor in the trough and so into the trough in which thefibre is deposited in a zig-zag manner. This ring-trough consists of asolid centre section 2 feet in diameter with a trough 0.5 feet wide and4 inches deep but integrally joined to it and is made of mild steel. Thering-trough contains a base of wire gauze 9 and revolves in a circulartrough l3 3 feet 4 inches external diameter, 1 foot 7 inches internaldiameter and 6 inches deep, also of mild steel fitted with an adjustableweir so that the height of liquor in the trough may be varied at will.The tow 3 sinks on to the base 9 of the trough i and is carried aroundwith the trough l which revolves once in 3 minutes. The tow 3 is takenup not less than 3 inches from the fibre met and is then mangled betweensqueeze rolls i i after which it is stretched between two godets l2 and[3.

The tow is now treated for 4 minutes in a solution containing 220 g./l.sodium sulphate, and 10 to g./l. formaldehyde at pH 5 and at 55 C.contained in the trough of a ring-trough 16 similar to the ring-trough 1and again according to the method described and claimed in patentspecification No. 623,460. This operation is effected by passing the tow3 from a godet l3 situated vertically above the centre line of thetrough of the said ring-trough I6 through a reciprocating spacing deviceI5. The tow 3 after leaving the trough of the ring-trough I6 is mangledbetween squeeze rolls l1 and passed from a godet l8 vertically downwardsaccording to the method described and claimed in patent specificationNo. 642,359 into the constant feed cone l9 where it is picked up by theinsolubilising liquid which enters the feed cone through a pipe 20 andis then carried through the tube 2| and a glass cone 22 into theinclined tube 23. The tube 2| is of inch diameter and the glass cone 22is 4 inches in diameter at the open end. The composition of theinsolubilising liquid is 340 g./l. sodium sulphate, 40 g./l. sodiumchloride, 270 g./l. sulphuric acid and 10 to 15 g./1. formaldehyde, andit enters the tube 23 at 90 C., and overflows at 85 C. The speed of theliquid flowing through tube 2| is controlled by the difference in levelsof the liquid at the inlet cone I9 and the overflow at the exit end ofthe tube 23 which in this case is 4 inches. The tube 23 is of glass 6inches in diameter and 8 feet long inclined so that the exit end israised 14 inches above the inlet end. At the exit end of the tube 23 isattached a perforated lip 24 made of lead Which raises the level of theliquid in the tube 12,3 and allows aitrto -flow away:without giving risetoilocal. regions iof high speed fiow. :On entering the incl ned tube123through the funnel .22 the tow forms a loose column about 4 feet longagainst :the'upperjsurfaceof the tube 23 filling roughly about of thecross sectional area and is .then removed at the exit end by the godet25. The peripheral speed of this godet is so adjusted that the time ofpassage through the tube 23 is constant and around minutes, whichis jWhat Ijclaim-isr q *1. n process -of insolubilizing'at least un'tlrthefilaments do not dissolve in a bath containing 0.1% sulfuric acid and0.25% sodium sulfate when immersed therein for 90 minutes at 97 C.,under conditions substantially free from tension, a continuoustravelling tow of protein filaments obtained by spinning aqueousalkaline solutions of proteins selected from the group consisting ofvegetable seed globulins and phospho-proteins into a sulfuricacid-sodium sulfate coagulating bath, said process comprising the stepsof relaxing said tow of coagulated filaments by impregnating the samewith an aqueous solution which contains at least 220 grams of sodiumsulfate per liter of solution, and is substantially free of sodiumchloride, thereafter impregnating the thus relaxed tow at a temperatureup to C. with an aqueous formaldehyde solution having a pH of between 4and 7 which contains at least 210 grams of sodium sulfate per liter ofsolution and is substantially free of sodium chloride and thereafterimpregnating the tow at a temperature between 70 and 98 C. in a stronglyacidified. aqueous formaldehyde solution containing, per liter ofsolution, at least 340 grams of sodium sulfate, at least 15 grams ofsodium chloride and at least 200 grams of sulfuric acid said processtaking from one to thirty minutes.

2. A process of insolubilizing at least until the filaments do notdissolve in a bath containing 0.1% sulfuric acid and 0.25% sodiumsulfate when immersed therein for minutes at 97 C., under conditionssubstantially free from tension, a continuous travelling tow of proteinfilaments obtained by spinning aqueous alkaline solutions of proteinsselected from the group consisting of vegetable seed globulins andphospho-proteins into a sulfuric acid-sodium sulfate coagulating bath,said process comprising the steps of relaxing said tow of coagulatedfilaments by impregnating the same with an aqueous solution whichcontains 220 grams of sodium'sulfate per liter of solution, and issubstantially free of sodium chloride, thereafter impregnating the thusrelaxed tow at a temperature between 40 and 80 C. with an aqueousformaldehyde solution having a pH of between 4 and 7 which contains 210grams of sodium sulfate per liter of solution and is substantially freeof sodium chloride and thereafter impregnating the tow at a temperaturebetween 70 and 98 C. in a strongly acidified aqueous formaldehydesolution containing, per liter of solution, 340 grams of sodium sulfate,15 grams of sodium chloride and 200 grams of sulfuric acid said processtaking from one to. thirty minutes.

3. The method of claim 1 wherein the aqueous formaldehyde solution whichcontains at least 210 g. sodium sulphate per litre of solution has atemperature of between 40 and 80 C.

4. The method of claim 1 wherein the said strongly acidifiedformaldehyde solution is used at temperatures between 90 and 98 C.

sufficientf toinsolubilise the protein filaments 5. The method-of claim[wherein the'tre'ating solutions preceding the said strongly acidifiedReferencee Cited in the file o this patent UNITEDYSTATES PATENTS Number1 Name i Date;

2,533,297 Thomson Dec. 12, 1950 2,565,908 Campbell et a1 Aug. 2a, 1951Tetlow Aug. 28, 1951 FOREIGN PATENTS Country Date Great Britain Sept.21, 1939 Great Britain Jan. 27, 1948 Great Britain May 18, 1949 OTHERREFERENCES Journal of Society of Dyers and Colorists, June 1945, pages150 to 155.

1. A PROCESS OF INSOLUBILIZING AT LEAST UNTIL THE FILAMENTS DO NOTDISSOLVE IN A BATH CONTAINING 0.1% SULFURIC ACID AND 0.25% SODIUMSULFATE WHEN IMMERSED THEREIN FOR 90 MINUTES AT 97* C., UNDER CONDITIONSSUBSTANTIALLY FREE FROM TENSION, A CONTINUOUS TRAVELLING TOW OF PROTEINFILAMENTS OBTAINTED BY SPINNING AQUEOUS ALKALINE SOLUTIONS OF PROTEINSSELECTED FROM THE GROUP CONSISTING OF VEGETABLE SEED GLOBULINS ANDPHOSPHO-PROTEINS INTO A SULFURIC ACID-SODIUM SULFATE COAGULATING BATH,SAID PROCESS COMPRISING THE STEPS OF RELAX-